Abstract
Abundant fossils of a single conifer species occur in a Pennsylvanian‐age deposit of eastern North America, providing the opportunity to describe a biological taxon of primitive conifers as well as to clarify the uncertain taxonomy and systematics of walchian conifers. Thucydia mahoningensis gen. et sp. nov. is represented by up to three orders of interconnected vegetative and fertile shoots that are preserved as coalified compressions with cuticles; some also display internal anatomy. The plant has an orthotropic stem, with two orders of plagiotropic lateral branches that all bear helically arranged simple leaves. Ovulate fructifications consist of compact zones of bracts with axillary ovuliferous dwarf shoots on otherwise vegetative branches. Pollen cones are compound shoots comprising helically arranged dwarf shoots in the axils of bracts on a main axis. Polliniferous dwarf shoots produce sterile scales, sporophylls with a terminal pollen sac, and in situ Potonieisporites grains. Stems have an endarch ...
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